Science fantasy is a mixed genre within the umbrella of speculative fiction which simultaneously draws upon and/or combines tropes and elements from both science fiction and fantasy. In a science fiction story the world is scientifically possible, while a science fantasy world contains elements which violate the scientific laws of the real world. Nevertheless the world of science fantasy is logical and often is supplied with science-like explanations of these violations.During the Golden Age of Science Fiction, the fanciful science fantasy stories were seen in sharp contrast to the terse, scientifically plausible material that came to dominate mainstream science fiction typified by the magazine Astounding Stories. Although at this time, science fantasy stories were often relegated to the status of children's entertainment, their freedom of imagination and romance proved to be an early major influence on the "New Wave" writers of the 1960s, who became exasperated by the limitations of "hard" SF.Eric R. Williams lists the following "microgenres" which can belong to science fantasy: Discovery, Dying Earth, ET Relations, Mad Scientist, Space Opera, Sword and Planet. Carl D. Malmgren classifies science fantasy by the type of the violation of science and discusses the following main types: the time loop motif, the alternate-present world, the counterscientific world, and the hybridized world.